In JavaScript, if you try to access a property of an undefined or null value, it will throw this error.
Here’s an example to illustrate this error:
var obj = undefined;
var header = obj.headercell; // This line will throw the error
In the above example, we have declared a variable named “obj” and assigned it the value undefined. When we try to access the property “headercell” of the undefined “obj”, it throws the mentioned error.
To fix this error, you need to ensure that the object is defined before trying to access its properties. Here’s an example of how you could prevent the error:
var obj = {
headercell: 'value'
};
var header = obj.headercell; // No error here
In the updated example, we have defined the object “obj” and assigned it a value that includes the property “headercell”. Now, when we try to access the property, it does not throw any error.
It’s important to check if an object is defined before accessing its properties using methods like “typeof” or “null” check. For example:
var obj = undefined;
if (typeof obj !== 'undefined') {
var header = obj.headercell; // No error here
}
In this example, we use the “typeof” operator to check if “obj” is not undefined before accessing its properties.
Remember to handle cases where the object is expected to exist but is undefined or null to avoid this error and ensure smooth execution of your code.